The present invention provides a new and improved method and apparatus for forming an improved cable.
Fiber optic cables have previously been manufactured by a process which involves twisting successive layers of glass fibers around a core. A moisture barrier may be formed by applying a coating of a grease-like sealant, over the glass fibers. A shield of corrugated metal tape is wrapped around the sealant coated glass fibers. The cable is then covered with a water impervious sheath. The sheath may be applied by extruding a polymer material around the outside of the cable.
In order to resist moisture flow along the cable in the event of a cut or break in the sheath, a swelling tape is wrapped around the glass fibers before the outer sheath is extruded around the cable. This swelling tape is a fibrous material that has some superabsorbent powder entangled in the fibers. A test that may be run to determine the ability of the cable to resist the permeation of moisture involves cutting the sheath and immersing the cable in water for 24 hours. If the water does not permeate any further than one foot from the cut, the barrier is considered to be adequate The addition of the swelling tape is relatively expensive.
It has been suggested that the superabsorbent material be mixed in the grease-like sealant which is applied to the glass fibers. The amount of superabsorbent material mixed in the sealant and the extent to which the sealant and superabsorbent material must be mixed is subjective and subject to human error. This may result in the use of excessive superabsorbent material and/or uneven mixing of the superabsorbent material with the sealant.